Divers can take on a wide range of tasks; underwater search and rescue, reconnaissance and salvage, demolition and construction, research or recreation. These tasks are complicated by the wide variety of conditions that they may be faced from shallow coastal tropical water and freshwater estuaries to deep ocean, arctic and ice covered ocean and timeframes that may be measured from minutes to days in the case of deep submergence and saturation diving as well as the desire to utilize communication systems.
Studies have shown that the difficulties of operating in these hazardous conditions are exacerbated by high levels of noise from a variety of sources both above and below the surface of sufficiently high intensity as to cause auditory damage. Typical sources in the divers' working environment might be blasts due to demolitions or repetitive noises due to underwater tools. In addition, self-generated noise such as airflow through a demand-regulator or the free flow air train can produce unacceptably noisy conditions. Divers are routinely exposed to a range of noise sources of sufficiently high intensity to cause auditory damage. Damage can be caused by high intensity short term exposure, but long-term exposure to levels exceeding 85 dB will cause hearing loss as well. Sources of damaging noise include:                self-generated breathing/helmet noise        ambient dive-site noise        tool noise        
All of these sources depend on the environment and/or the diver responses. Even the self-generated breathing noise is impacted by the exertion level of the diver and can rise to damaging noise levels if physical activity and air demand are high. Acoustic levels of communications must exceed all background noise levels to be effective. Communications can actually produce more damage than other noise sources. Reducing other noise sources is critical to overall diver helmet sound levels. Some of these noise sources are common in self contained breathing apparatus (SCBA) and abrasive blasting hoods as well.
Needs exist for improved noise reduction and improved communication in helmets and SCBA and other breathing devices. Pilots and other helmet wearers would be benefited by improved noise reduction and communication in helmets.